The overall aim of this research is to introduce an innovative approach to increase physical activity in schools, and thereby, decrease risk factors for type 2 diabetes in children and adolescents. Since very little is known about the fundamental interrelationships among fitness, body composition, and physiological markers of glucose homeostasis in growing children, the research is also aimed at filling key gaps in this knowledge base. The Specific Aims of the proposal are to develop, implement, and test the effectiveness of: a school-based physical activity enhancement program, Fitness Laboratory On Wheels (FLOW); and a complementary school-based teacher/student education program to enhance physical activity and reduce sedentary behaviors. A prospective, repeated-measures, exercise-intervention/control study is planned. The intervention will span the 7th and 8th grades with an additional two-year follow-up. To test the specific effects of the exercise program per se, but recognizing as well, the role of diet in ameliorating the risk of type 2 diabetes, a nutrition education program will be implemented in both control and exercise intervention schools. The following hypotheses will be tested: the two-year intervention will lead to (1) Improved insulin sensitivity and/or improved recovery from the natural fall in insulin sensitivity that occurs during puberty; (2) An increase in physical fitness by at least 10% (accounting for natural growth and development) and enhanced physical activity behaviors; (3) Improvement in anatomic markers of type 2 diabetes risk; (4) Improvement in novel biochemical markers associated with diabetes risk; and (5) A sustained ;improvement in these variables for at least 2 years following the intervention. Major outcome variables include: "traditional" markers of glucose homeostasis - fasting insulin and glucose (all subjects) and insulin sensitivity, glucose effectiveness, and acute insulin response (sub-study with frequently sampled intravenous glucose tolerance test - FSIVGTT); novel markers of type 2 diabetes risk - growth hormone binding protein (GHBP), insulin-like growth factor binding protein-1 (IGFBP-1), and tumor-necrosis factor-alpha (TNF-alpha); peak oxygen uptake from ergometer exercise tests; body composition by dual x-ray absorptiometry (DEXA); and psychosocial tests of exercise-associated behaviors. A physiological assessment protocol that would be both feasible and fun for the majority of volunteers was successfully pilot tested. It was demonstrated that in a single morning, groups of children can be transported from a target school to an available clinical research center and comfortably undergo a testing strategy called "BEDD" [(1) fasting blood sampling, (2) exercise testing, (3) DEXA measurements of body composition, and (4) diet recall]. Power analysis based on fasting insulin levels in healthy children suggests that a multi-center study (3-4 centers with 4-5 schools per center) would be needed to achieve these aims.